Flexible valve diaphragm



Nov. 13,1923.

W. T. MIXSELL FLEXIBLE VALVE DIAPHRAGM Filed July 2G. 1922 2 Sheets- Sheet 1 lll Patented Nov. 13, 1923,

PATENT OFFICE.

WARD T. MIXSELL, OF CUMBERLAND, MARYLAND.

FLEXIBLE VALVE DAPHRAGM.

Application filed July 26,

To all whoml f may con cern.'

Be it known that l, WARD T. MixsELL, a citizen of the United States, residing at Cumberland, in the county of Allegany and State of liblaryland, have invented certain new and useful improvements in a Flexible Valve Diaphragm, of which the following is a specification.

lVly invention relates to the art of fabricatino; articles made of a composite structure of fabric, or the like, preferably molded in intimate union with an elastic medium such as vulcanizable rubber compounds, or the like.

My inventionv will be best comprehended and properly related to the art to which it belongs if specifically described Vas a. flex ible molded diaphragm, made in a new and novel manner; all as more fully set forth hereafter.

Flexible diaphragme have a wide range of usefulness; among the more common of which may be cited t-employment as a substitute for the usual tight-fitting' piston within a cylinder utilize-d as a liquid pumping,` device; and in conjunction with equalizer or compensating` valves, wherein the diaphragm transmits a fluid pressure against a suitably counterbalanced free-moving piston head for the purpose of actuating appropriate dependent mechanism for accomplishing' a regulatory function. There are, of course, otherand varied uses to which this basic type of diaphragm is put under existingr engineering` practices; also there are likely to be many new ruses resorted to under the termsof the additional efhciency imparted to this type of diaphrag'm by my present disclosure. l, therefore, do not attempt to prescribe any limitations of utility for my device, but merely select some well known uses of prior types of diaphragms by way of illustration and as affording` a basis fon-comparing the ellie ciency and novelty of my invention with those other types heretofore used and .known in the prior patented art.

Selecting', by way of illustration, the usual compensator or equalizer valve diaphragm in its conventional environment, it isapparent that the article must possess a high de` ,aree of flexibility without fatigue; for the diaphragm is seldom at rest, being in almost constant pulsation as the pressure on either 1922. serial No. 5772671.

side fluctuates. In addition to flexibility, maximum strength consistent thereto is required, as in many instances it is advisable to lit reducing' controls on high pressure lines wherein direct pressures in excess of two hundred pounds per square inch are encountered.

In the past'it has been the universal practice to construct diaphragms of rubber or rubber compounds without fabric or cordage reinforcement,A whereby they attain the desired degree of flexibility, lbut only at the expense of being too weak for any than low pressure work; or, to build them up of plies of conventional cross-woven fabric or crosslaid cordage, usually impregnated with a vulcanizable rubber solution, with or without interposed sheets of rubberthe assembled struct-ure being thereafter subjected to the well known molding operation.

The cross-woven insert fabric diaphragms Vpossess inherent weakness due to inequality of stress in the component strands, accounted for by the fact that those relatively few strandsV that cross the center of the disk structure with extremities effectively anchored on the bolted periphery, have their entire lengths free to flex when the diaphragm distorts under pressure, whereas, the shorter strands, farther removed from the center, are necessarily restricted in their amplitude of flexation in proportion to their effective lengths. The practical consequence of this inherent defectis that the work is necessarily done by a relatively few short members which break down prematurely thereby rupturing the diaphragm before the longer elements have exerted their influence.

Recognition of this inherent tendency of cross-woven insertions to break down prematurely has led to the universal practice of incorporating into the structure a suflicient number of plies to meet the stresses encountered. This excessive thickening of the structure carries with it undue stiffness, whereby the diaphragm is wholly unable to accommodate the desired response to slight pressure variations, to the detriment of the proper functioning of the device of which it forms the controlling element.

It has also been demonstrated that any flexation of a disk diaphragm composed of cross'lwoven insertions is attended by a 'method of construction is not justifiable in view of vthe equally effective and less expensive methods disclosed hereafter; If it be desired to adhere to this method of intact cords from periphery to center and yet avoid overlapping at the center, it is obvious that individual radial cords could be assembled in flat abutting relation at the center and thence radiate to the periphery in uniformly divergent relation. Between the diverging cords additional cords, stopping short of the center, could be placed and the whole lightly spun together in an appropriate manner; the

Whole suitably overlaid with a vulcanizable binder and molded in the usual manner.

'In view of the expense involved in practicing the method of Fig. l, and further considering the fact that the cord stock therein used could only be coated or frietioned at considerable expense and inconvenience, preference is expressed for the construction disclosed in Fig. 2. This practice permits the utilization of commercially prepared and previously frictioned cord fabric, cut into appropriate segments and assembled between layers of vulcanizable rubber in single ply in abutting relation, and thereafter molded and vulcanized in the usual manner. In this type, during the molding, there is a tendency of the segments to open up along their abutting edges When the overlaying rubber sheets are in flow under heat and pressure; thereby creating a certain element of Weakness, to overcome which the construction disclosed in Fig. 3 is preferred.

The construction of Fig, 3 completely eliminates the Weakness due to the spreading of the single ply segments. In this method a plurality of plies, each of abut- Vting segmental form, are overlaid with their respective edges staggered; thus resulting in the ultimate strength of the diaphragm being increased in proportion to the number of plies, and making a structure that molds up into an efficient iat product.

The segmental, single ply, edge lapped structure of Fig. Ll, illustrates the attainment of a high degree of radial strength attained by extending a greater number of intact cords from center to periphery than obtains in the method of Fig. 2, andwith the use of but a small additional amount of cord stock. This method eliminates the necessity and expense of the two-ply system disclosed in Fig. 3, and the Weakness developed by the existence of interstices between abutting segments as cited in discussing Fig. 2. In laying up this method, the apex of the several segments are made relatively broad in order that virtually a double ply is attained at the center, Whilel at the periphery the adjacent segments present but a single ply dueto the termination of the overlap Vof the edges. Each successively laid segment overlaps a portion of its neighbor, as shown in Fig. 4, whereby the short parallel cords of each separate segment, terminating progressively short of the center, overlay and vreinforce each other in a. manner tending to resist lateral separation under molding pressure and unify the structure to resist radial stresses. The overlapping blunt ends of the apex of each segment contain a num-` ber of full length cords presenting, in the aggregate, a most effective distribution of strength elements, Such a diaphragm is particularly flexible and radially strong.

In Fig. 5 is shown a variation of the basic system disclosed in Fig. f4, but so overlapped that at least a double ply of cords Will be attained at the lperiphery, 'and the multiple .overlapping of the apex ends Will insure that the proportionate strength Will be maintained throughout. This diaphragm will withstand extreme pressures, and yet be much more flexible at the point of greatest flexation than a correspondingly strong diaphragm made of conventional cross-Woven fabric.

.It will be appreciated that these flexible diaphragms are subjected to unusually severe conditions and 'that they are concealed parts, Working constantly under conditions that do not admit of periodic inspeetion'for the purpose of ascertaining their nearness to failure. Their failure, in the average installation, is a costly and inconvenient occurrence, It will thus be appreciated that any improvement, however slight, becomes of great significance to the large engineering field Within Which they find a place.

By reference to Figs. l0 and 11, it is noted that the zone of greatest fatigue occurs in the circular area at or about the periphery of the floating piston head V17.

vAbout this line of resistance all diaphragms of the cross Woven fabric type develop a well defined circular buckle at an early stage of' their service; the time and seriousness of this deformation, of course, depending upon the character of the service and the pressures encountered, The constant working about this point soon breaks dmvn the conventional diaphragm. whereas inthe present invention exhaustive tests have proved that the lines of strength cords` be ing radial and therefore normally at right. angles to the fatigue Zone about the piston. resistY the buckling action most successfully and practically eliminate the otherwise fatal Weakness at this point. The dotted lines in Fig. 10 indicate the depressed piston when the pressure on the primary source has dropped until the counterbalancev has deflected the piston; and in this condition the tendency of the diaphragm tto crease or registered.

buckle about the piston edge n the upstroke is best appreciated.

The radial strength elements could be made of any material that is relatively inextensible, for instance, woven wire, instead of conventional cordage; -provided, such material be Capable of considerable flexation without fatigue. The neutral position of the/diaphragm shown in Fig. X, illustrates the peculiar circumferential wave that forms about the periphery of the piston-restrained diaphragm at each pulsation. At this point fatigue tendency is high, and it is here that cross-woven fabric of the prior art shows fatal weakness. By the rz dially directed method of fabricating the strength elements this fatigue point is eliminated as a source of trouble, for the obvious reason that each radial member is free to adjust itself circumferentially with respect to adjacent members by a slight resilient separation at the expense of stretching the elastic binder, thus compeneating for the relative circumferential adjustments between the elementswithin the zone of disturbance, without rupture. The conventional cord fabric. impregnated with a rubber solution prior to cutting and fabrication into the diaphragm, is peculiarly adapted to negative this buckling fatigue, for each cord is practically insulated by a film of resilient compound whereby separation of cord-from-cord in circumferential adjustment is made possible.

Test observation of cross-woven fabric diaphragms in competition with my radial cord structure, where the same weight of fabric insertion strength elements are employed, has conclusively demonstrated the vast superiority of the latter, not only as measured bv length of service,l but of greater moment, by the ultimate breaking stress ln test vthe cross-woven type lalmost invariably fails prematurely along the piston periphery zone, showing the parting of the transverse elements in ad- Vance of the failure of the few radially directed strands. On the other hand, the radial cord type shows transverse rupture at almost any radial point between the center and the bolted periphery, showing that the strength elements are uniformly stressed and that. no unnecessary material is incorporatedjinto the article.

llaving now described my invention what l' claim is:

l.. A flexible diaphragm of the class de scribed` comprising a circular' disk fabricated ofradially directed strength inenibers enrbedded in a unifying binder.

2. A flexible diaphragm of the class described, comprising a circular disk fabricated ofradvially directed strength members em` bedded in a unifying, elastic vulcanized blinder.

with a rubber solution Vwhereby they areV practically insulatedA from each other.

it. Afllexible diaphragm of the class described, comprising a relatively thin, flat body falnficated of strength members directed towardpa common center and embedded `in an elastic binding medium of vulcanized ,n1ateuial.. f

A flexible` diaphragm of the class de scribed, comprising a. disk-like body fabricated of textilev cord-li-ke strength elements, radially directed and embedded in an elastic binding medium. y

6. .A prcssureresisting flexible diaphragm of the .class` described, comprising substantially radially directed strength elements embedded between layers of an elastic vulcanized binding medium.

7. A pressure-resisting flexible diaphragm of the class described, comprising radially directed strength elements bonded in an elasf tie vulcanized medium whereby lgreater extensibility circumferentially than radially is atta.ined. y i i 8. A pressure-resisting flexible diaphragm of the class described, comprising strength members of cord laid in substantially radial relation in a vulcanized binder having greater resilient properties than vsaid cord members.

9. A pressure-resisting diaphragm of the class described, comprising a plurality of segmental sections of parallel strength members ruiming in the direction of thel length of the said sections, said sections being assembled in theform of a circular disk whereby the said strength members are substantially radial, and embedded in an elastic vulcanized binder whereby, the assembled article is unified by a molding operation. y 10.` A pressure-resisting flexiblevk diaphragm, coinprising a plurality of relatively narrow segmental sectionsv composed of parallel strength members, said sections being assembled andinolded in union `between sheets of an elastic vulcanized medium with the strength members in substantial radial relation.

1 1. A pressure-resistiug flexible diaphragm, comprising a plurality of relatively narrow segmental sections composed of paralle] strength members, said sei-tions being assembled yin superposed radial relation whereby aplurality of intact strength members extend substantially radially from the center of the diaphragm to its periphery and moldedlin union with an elastic vuleanizedA binder. l i

Ak pressurerresisting. flexible, diaf phragm, comprising a` plurality of relatively narrow segmental sections composed of parallel strength members, said sections being overlappingly assembled in approximately radial relation With the overlap progressively increased toward the center whereby numerous intact strength members are maintained from centertc periphery.

i3. The combination with a regula-tory device comprising a lined body and a moving balanced part, of a iiexible diaphragm comprising a vulcanized disk composed of radially directed strength members carried in a .vulcanized binder, said diaphragm being suitably anchored to the fixed body and the II moving part whereby the moving part is actuated by fluctuating pressures on either side of said diaphragm.

14:. The method of fabricating a flexible circular diaphragm, consisting of the following steps: a., impregnating cord fabric with a vulcanizable rubber solution; b, cutting the impregnated fabric into segmental sections and laying them in intimate relation 

